In a polymer electrolyte fuel cell (PEFC), hydrogen ions (H+) pass through a solid polymer electrolyte membrane, so the electrolyte membrane must constantly be kept in a wet state. A fuel cell power plant using a fuel cell of this type operates while supplying water to the electrolyte membrane. Therefore, the fuel cell contains a considerable amount of water, and if the power plant is left below freezing in the stationary state, the water in the fuel cell including the water in the electrolyte membrane will freeze. Consequently, in order to start the fuel cell power plant below freezing point, the ice in the fuel cell must first be thawed.
In this regard, Tokkai 2000-315514 published by the Japanese Patent Office in 2000 discloses an apparatus wherein high temperature gas from outside is supplied to a gas passage in the fuel cell to thaw the ice in the cell.